Type L Hangars, Site E, Crudwell, Wiltshire

Description

CRUDWELL

1360/0/10026 KEMBLE BUSINESS PARK
07-MAY-10 KEMBLE BUSINESS PARK
Type L Hangars, Site E

GV II
Two aircraft storage hangars. 1939, to Air Ministry Directorate of Works and Buildings drawing Nos 5163-5/39. Steel rib framework, concrete roof on pressed metal sheeting, asphalt roof covering; in-situ concrete end walls.

PLAN: The hangars are identical, set roughly but staggered, and approx 730m south of the W end of the main runway. Each a plain rectangle, internal dimensions 300 x 167 x 36ft maximum height (91.4 x 50.8 x 11.1m); they form a low parabolic vault springing from ground level, and at each end wide doors; at the inner ends are attached annexes, one with the boiler room and small doors give access for personnel.

EXTERIOR: A broad expanse of asphalt covering the low-profile parabolas is completely unbroken. The outer end walls, which reduce in thickness at about half-height with an external offset, contain four wide steel doors in a plain rectangular opening; above the centre is a steel tube ventilator or stack. The inner ends, with a similar reduction in wall thickness at half-height, has similar wide doors, with to the left a shallow boiler-house annex attached to and parallel with the wall, and a square stack rising just above parapet height. To the right is a smaller shallow annex. The parapet ends are flared out at the bottom; a continuous wide concrete trough-gutter runs at ground level along each side.

INTERIOR: The floor is smooth finished concrete. The structure is a series of triangular-section fabricated steel ribs carrying profiled sheet steel as formwork to the poured concrete roof. A series of continuous longitudinal steel rails is suspended from the ribs.

HISTORY: This form of hangar is evolved from the earlier 'Lamella' type (qqv Sites A and B), with the same overall dimensions, but with easily prefabricated steel ribs, set in parallel, to carry the concrete roof. Originally the roofs were covered in earth finished in turf; this provided some extra protection against bomb blast, but also created excellent camouflage from above. Turf-covered versions may be seen at Hullavington Airfield (Wiltshire), about 10km S from Kemble. Kemble, by virtue of its range of 5 different hangar types including structurally advanced ones of parabolic form, is the most outstanding and strongly representative of the 24 Aircraft Storage Units planned and built by the Air Ministry for the storage of vital reserve aircraft in the period 1936-1940. The ASUs were all administered by Maintenance Command and were sited to the W of the principal bomber stations and fighter belt, and their function was to receive and store aircraft before they were made ready to be sent to operational bases: some, such as Hullavington to the south, were grafted onto existing Flying Training Schools.

Apart from a cluster of 3 hangars on the Main Site, the hangars were planned in pairs around the flying field. The planners of ASUs thus exercised, for the first time, the principle of 'dispersal' in the planning of military airfield landscapes as opposed to fabric, the planning of domestic and technical sites having integrated these requirements from the 1920s. The dispersal of aircraft around the flying field, instead of being concentrated in the hangars, provided further protection against air attack (particularly crucial for the vital supplies of reserve aircraft to front line units) and had a profound influence on airfield layout during the Second World War. This principle also had an effect on hangar design in ASUs, in the use of both concrete and roofs of parabolic form - the latter originally turfed over for additional protection - which housed aircraft in the 'tails-up' position hung from their roofs.

The Type D hangar, which combines concrete construction with bow-string trusses, owes its origin to developments in French engineering (as for example at the historic Montaudron airfield at Toulouse). The genesis of the parabolic Lamella type of hangar is the Lamellendach technique, produced by Junkers in Germany from the early 1920s, which utilised a structural grid of short and small-scale steel sections in a diagonal grid in order to create a parabolic vault. This type of hangar was built in England under licence from 1929, and there are four at Kemble (Sites A and B). In addition there are two variants in construction, using the same overall form and dimensions but developed differently: Type L uses close-spaced concrete ribs formed in pressed steel members (Sites F (not included) and E) and Type E uses ribs of small-section steel to support concrete slabs curved to the arc of the frame (Site C). These steel and concrete rib hangars most clearly relate to contemporary experimentation elsewhere in Europe, especially Pierre Luigi Nervi's Lamella-derived forms built for the Italian air force, the Zeiss-Dwidag concrete-ribbed vaults used for side-opening hangars in Germany and the concrete hangars developed for the French air force from the 1920s. All these hangar buildings stretched existing engineering technology in order to clear wide spans, forming the basis for developments in the post-war period. The existence of such a variety of these types of hangars at Kemble, also relating to an advanced type airfield landscape, is certainly unique in a British context, and no such group survives in France or Germany.

RAF Kemble was officially opened in June 1938, but construction continued into 1939 and a Station HQ was not formed until October 1940, under 41 Maintenance Group. By November over 900 personnel were involved, many of them civilians, staffing the Maintenance Unit: most were accommodated off-site, and others were in hutted units, mostly in Kemble Wood to the E. The daily amount of aircraft stored in October was 330, from antiquated Hawker Harts to Bristol Beauforts, Blenheims and Hurricanes. Two runways were built between September 1941 and April 1942, the main one being extended in 1943 in order to accept heavy bombers and accompanied by the building of new taxiways. The station survived aerial attack in 1940/1, it going on to play an important role in the readiness for D-Day with work on Horsa gliders and Typhoons in early 1944. The Fosse Way crosses the site.

SOURCES: The Royal Air Force Builds for War: A History of Design and Construction in the RAF, 1935-1945, (1956, republished by HMSO 1997), 290-302
Operations Record Book, Public Record Office AIR 28/218
Ashworth, C: Action Stations 5 (Military Stations of the South-West) (1982), 115-7
Allen, J S: 'A short history of 'Lamella' construction', Transactions of the Newcomen Society, 71 (1999-2000), 1-29

REASONS FOR DESIGNATION: The pair of Type L hangars at Site E on Kemble Airfield, constructed in 1939, are designated at Grade II, for the following principal reasons:
* Architectural interest: these structures are part of a significant evolution in the design of hangars in the period, and are well-preserved examples
* Historic interest: Kemble, by virtue of its range of five different hangar types including structurally-advanced ones of parabolic form, is the most outstanding and strongly representative of the 24 Aircraft Storage Units planned and built by the Air Ministry for the storage of vital reserve aircraft in the period 1936-1940
* Group value: the Type L hangars form part of a wider complex with the other contemporary hangar groups dispersed around the airfield, reflecting a development in the strategic planning of military airfields in the period

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Type L Hangars, Site E

A Grade II Listed Building in Crudwell, Wiltshire

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